Night and Day on ? Pictoris b

Writing yesterday about Kevin Luhman’s discovery of another cold brown dwarf in the stellar neighborhood reminded me of work we discussed earlier this year in which the weather on the surface of Luhman 16 B was mapped. This was done using the European Southern Observatory’s Very Large Telescope (see Focus on the Nearest Brown Dwarfs), which found variations in the brightness of one of the two dwarfs in this interesting binary just six light years from the Sun. We are beginning, in other words, to chart features in the atmosphere of a brown dwarf whose atmosphere is 1100 degrees Celsius and filled with molten iron and minerals.

With that in mind, the news that Dutch astronomers also using the Very Large Telescope (with the CRIRES spectrograph) had measured the rotation rate of an exoplanet immediately caught my eye. Beta Pictoris b orbits its primary some 63 light years from Earth in the constellation Pictor (The Painter’s Easel). It was one of the first exoplanets to be directly imaged and, at a distance of 8 AU, the closest exoplanet to its star that has ever been imaged. Now we learn that the equatorial rotation velocity of the planet is almost 100,000 kilometers per hour.

Bear in mind that Beta Pictoris b is about 3000 times more massive than the Earth and some sixteen times larger, yet a day on this world lasts a paltry eight hours. We can contrast that with Jupiter’s equator, whose cloud cover rotates at 47,000 kilometers per hour, or with the Earth, whose rotation rate is a comparatively puny 1674.4 kilometers per hour. What we’re seeing here is an extension of the relationship between mass and rotation that we’ve already observed in the Solar System. Remco de Kok is a co-author on the paper announcing the find:

“It is not known why some planets spin fast and others more slowly,” says de Kok, “but this first measurement of an exoplanet’s rotation shows that the trend seen in the Solar System, where the more massive planets spin faster, also holds true for exoplanets. This must be some universal consequence of the way planets form.”


Image: This graphic shows the rotation speeds of several of the planets in the Solar System along with the recently measured spin rate of the planet Beta Pictoris b. Credit: ESO/I. Snellen (Leiden University).

That we could make such measurements of this young world (Beta Pictoris b is about 20 million years old) is an indication of advancing techniques similar to those that brought us the weather on Luhman 16B. The researchers, from Leiden University and the Netherlands Institute for Space Research (SRON), studied changes in the wavelength of received light to detect the different speeds and direction of different parts of the planet. This was exquisitely challenging work in that it involved separating this already tiny signal from the light of the parent star.

The team’s variation on Doppler imaging allowed measurements of the wavelengths of radiation from the planet to a precision of one part in 100,000, enough to detect the velocity of the various parts of the planet’s atmosphere that are emitting light. “Using this technique we find that different parts of the planet’s surface are moving towards or away from us at different speeds, which can only mean that the planet is rotating around its axis,” adds lead author Ignas Snellen.

We can imagine future work not only in creating a global map of Beta Pictoris b’s cloud patterns but, with the help of the upcoming European Extremely Large Telescope (E-ELT) and its planned METIS spectrograph and imager, maps of exoplanets much smaller in size. For now, though, Beta Pictoris b may remain the target of the team’s near-term studies. From the paper:

The SNR [signal-to-noise ratio] that can be achieved on a planet spectrum for this type of observation is a strong function of telescope diameter D. This opens the way of obtaining two-dimensional maps of the planet using Doppler imaging, a technique used to map spot distributions on fast-rotating active stars. Very recently, a first Doppler image map was produced for the nearby brown dwarf Luhman 16B (K=9.73) using CRIRES on the VLT, showing large-scale bright and dark features, indicative of patchy clouds. The planet ? Pictoris b is only a factor 13 fainter than Luhman 16B. Our simulations…show that a similar study can be conducted on ? Pictoris b using future instrumentation.

The paper is Snellen et al., “The fast spin-rotation of a young extra-solar planet,” to be published online in Nature 1 May 2014.


Luhman’s Latest: A New, Nearby Brown Dwarf

Kevin Luhman (Pennsylvania State University) has focused much of his research on the formation of low-mass stars and brown dwarfs in star-forming regions near the Sun. This involves working with relatively young stars, but Luhman is also on the alert for older objects, very cool brown dwarfs in the solar neighborhood. Brown dwarfs cool over time, and as Luhman describes on his university web page, they are ‘valuable laboratories for studying planetary atmospheres.’ They also give us a chance to test theories of planet formation in extreme environments.


Now we have Luhman’s latest, and it would not be a surprise if the whole category of nearby, cool stellar objects begins to get referred to as ‘Luhman objects’ or some such. Remember that it was just back in March that the astronomer discovered, using WISE images, a binary brown dwarf system at a scant 6.5 light years from Earth. The new find is WISE J085510.83-071442.5. It has the third highest proper motion and the fourth largest parallax of any known star or brown dwarf, and can lay claim to being, at least for a time, the coldest brown dwarf on record.

Image: Penn State’s Kevin Luhman, a specialist in low mass stars and brown dwarfs, who is filling in our map of such objects close to the Sun.

How cold? This object is thought to be between -48 to -13 degrees Celsius, colder than previous record holders, which were found to be close to room temperature. WISE imagery from 2010 was confirmed by two additional images taken by Spitzer in 2013 and 2014, with further observations at the Gemini South telescope on Cerro Pachon in Chile. The WISE and Spitzer data were used to measure the distance to the object via parallax. It turns out to be 7.2 light years away, fitting nicely into the chart below, which shows the Sun’s immediate neighborhood.


Image: This diagram illustrates the locations of the star systems closest to the sun. The year when the distance to each system was determined is listed after the system’s name. NASA’s Wide-field Infrared Survey Explorer, or WISE, found two of the four closest systems: the binary brown dwarf WISE 1049-5319 and the brown dwarf WISE J085510.83-071442.5. NASA’s Spitzer Space Telescope helped pin down the location of the latter object. The closest system to the sun is a trio of stars that consists of Alpha Centauri, a close companion to it and the more distant companion Proxima Centauri. Credit: NASA/Penn State University.

That’s a fascinating chart, and while all of us can share the determination to learn more about brown dwarf and planet formation and the atmospheres of cold objects, some of us also think in terms of targets for future probes, hoping that brown dwarf hunter Luhman may turn up something even closer than the three he has already discovered. Objects as cool as Luhman’s latest can all but disappear at visible wavelengths, but their infrared glow makes detection possible, with surely more to come. Thus Michael Werner, a Spitzer project scientist at JPL:

“It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun’s nearest neighbors. This exciting new result demonstrates the power of exploring the universe using new tools, such as the infrared eyes of WISE and Spitzer.”

We’re talking about an object somewhere between 3 and 10 times the mass of Jupiter, which makes WISE J085510.83-071442.5 one of the least massive brown dwarfs known, if indeed it is a brown dwarf rather than a free-floating gas giant that has been expelled from some undetermined star system. Luhman comments on the latter possibility in the paper on this work:

At this mass, WISE 0855?0714 could be either a brown dwarf or a gas giant planet that was ejected from its system. The former seems more likely given that the frequency of planetary-mass brown dwarfs is non-negligible while the frequency of ejected planets is unknown. Assuming that WISE 0855?0714 is a Y dwarf, the four closest known systems now consist of two M dwarfs and one member of every other spectral type from G through Y.


Image: This artist’s conception shows the object named WISE J085510.83-071442.5, the coldest known brown dwarf. Brown dwarfs are dim star-like bodies that lack the mass to burn nuclear fuel as stars do. WISE J085510.83-071442.5 is as cold as the North Pole (or between minus 48 to minus 13 degrees Celsius). The color of the brown dwarf in this image is arbitrary; it would have different colors when viewed in different wavelength ranges. Credit: NASA/JPL-Caltech/Penn State University.

The paper goes on to note that the newly discovered brown dwarf now offers the chance to test various atmospheric models in an unexplored temperature regime, something that will require refining the parallax measurement and ‘deeper near-IR photometry to better constrain its spectral energy distribution.’ We’ll also need to take advantage of near-term advances in our spectroscopy of the sort the James Webb Space Telescope should make available.

The paper is Luhman, “Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun,” The Astrophysical Journal Letters Vol. 786, No. 2 (2014), L18 (abstract / preprint). A JPL news release is also available.


Interstellar Conferences for 2014

2014 isn’t nearly as top-heavy with interstellar conferences as the year before, but we do have two to discuss this morning, both of them slated for fall in North America. Looking through the preliminary information, I’m remembering how many good sessions grew out of last year’s meetings. For a field that grew up fueled largely by the enthusiasm of individuals who met in person only rarely, we suddenly found ourselves with the 100 Year Starship conference in Houston, Icarus Interstellar’s Starship Congress in Dallas, two Starship Century events (one in London, one in San Diego), the Tennessee Valley Interstellar Workshop (version 2) and a London conference on what Bob Parkinson so wonderfully calls ‘the philosophy of the starship.’

Various smaller get-togethers occurred as well, and so, of course, did huge space-dominated conferences like the International Astronautical Congress and other aeronautics, astronautics and SETI sessions around the world. But who would have thought even ten years ago, much less fifty, that we would be having multiple conferences in a single year arranged around starship topics, and that groups dedicated to studying the possibilities of interstellar flight would be proliferating? A friend and I were musing that we found ourselves living in a science fictional world, and the thought came that it just seemed that way because we were getting older. And, of course, we are, but it’s also true that deep space really has become a highly visible topic.

100 Year Starship Symposium 2014


The theme for this year’s 100 Year Starship Symposium is Pathway to the Stars, Footprints on Earth, a nod to the synergies the organization continues to seek out between the huge advances in technology and biological science we’ll need as we anticipate deep space missions and the developing spinoff tools we’ll gain from such work to improve life on Earth today. The symposium will be held at the George R. Brown Convention Center in Houston from 18 to 21 September.

Although registration for the actual event has not yet begun, the call for papers is now active, with abstract submissions manageable through the symposium site. The deadline for abstracts is May 31, with notification of acceptance on June 30. Accepted presentations and poster submissions are then due on the 10th of September. Quoting from the submission guidelines:

Submissions can be perspectives on the central dogma, experimental results, and review of a specific topic. You must ensure that it fits the track topic to which you are submitting. Individual presentations will only be presented in one track. Individuals do not have to be associated with an institution to submit an abstract. Please note that materials should be non-commercial in content, any commercial presentation that communicates a service, technology or product can be submitted to our poster session.

Submissions will be reviewed based on bona fide field of inquiry/thought/research that derive from validated patents, literature, mathematics or practice. The data submitted should represent one or more of the following:

Actual data or background search generated presents a challenge to current dogma or asks a significant question

Data moves the field forward or clarifies some aspect of the field

Solves a problem acknowledged in the field

Provides a novel, well supported integration and/or review of field and proposes specific concept

Submitted abstracts are well written, 300 word, concise and includes a statement of the following items. If actual data, results and conclusions are not available, please provide a well thought out plan for how the information will be generated.


Problem and hypothesis

Experimental design (or literature review)



Conclusions and Discussion

The tracks are available on the symposium site. They range from propulsion and energy to near-term spinoff technologies, data, communications and information technology, and major issues of life support and sociology. The data and communication track is a new one, highlighting recent work on data retrieval and transmission at interstellar distances. Also new at the 2014 symposium will be a track on interstellar education, looking at the role of education at producing what the site calls ‘interstellar citizens’ and probing current and future educational practices. Poster presentations are available for discussions in a small group setting.

Tennessee Valley Interstellar Workshop

The third Tennessee Valley Interstellar Workshop will be held November 9-12 in Oak Ridge, Tennessee at the DoubleTree by Hilton Hotel with a theme of Long-Term Thinking–Present-Day Action. I’ve recently received the call for papers for this event, which was originally conceived by Les Johnson, Greg Matloff and Robert Kennedy in a wonderful hotel in the Italian alps in the town of Aosta. I remember the setting well, having spent several days there at one of the earlier Aosta conferences — it’s a place where long-term thinking seems to come naturally. Have a look at the TVIW website for further background, including Les’ summation of the event:

“The Tennessee Valley Interstellar Workshop is an opportunity for relaxed sharing of ideas in directions that will stimulate and encourage Interstellar exploration including propulsion, communications, and research. The ‘Workshop’ theme suggests that the direction should go beyond that of a ‘conference’. Attendees are encouraged to not only present intellectual concepts but to develop these concepts to suggest projects, collaboration, active research and mission planning. It should be a time for engaging discussions, thought-provoking ideas, and boundless optimism contemplating a future that may one day be within the reach of humanity.”

Presentation/paper and workshop topic submissions are now open through August 1, with the full papers and presentations due two weeks prior to the start of the meeting. Do note that this event is limited to 75 participants, with applications for attendance and further information about submissions made by email to A bit more from the call for papers:

Participants who do not wish to present a paper or facilitate a workshop will also be considered and are requested to submit a bio describing their involvement in the field of developing Interstellar concepts, including interstellar-related space science and technology and space advocacy. Submissions relating humanities, art and social sciences to interstellar exploration are also encouraged. Going to the stars will involve and engage most aspects of human society and innovation in all fields that may contribute are of interest. All Participants (including Presenters) are encouraged to bring a free-standing poster describing their Interstellar work, suitable for exhibition.

Presenters will be given thirty minutes to present their work including a Q&A session at the end, and it seems probable (though I haven’t confirmed this) that selected papers will be submitted to the Journal of the British Interplanetary Society for publication. Note, too, that on Sunday November 9, TVIW will conduct two seminars to which accepted attendees are invited, one a three-hour short course on space propulsion taught by Les Johnson, the other a course on terraforming, its methods and rationale, taught by Ken Roy. Registration for these seminars can be managed through the TVIW website once your attendance has been confirmed. Direct any questions about participation to


The Infrastructure Problem [1]

Nick Nielsen today tackles an issue we’ve often discussed in these pages, the space-based infrastructure many of us assume necessary for deep space exploration. But infrastructures grow in complexity in relation to the demands placed upon them, and a starship would, as Nick notes, be the most complex machine ever constructed by human hands. Are there infrastructure options, including building such vehicles on Earth, and what sort of societies would the choice among them eventually produce? You’ll find more of Nielsen’s writing in his blogs Grand Strategy: The View from Oregon and Grand Strategy Annex. In addition to his continuing work for the space community, Nick is a contributing analyst with strategic consulting firm Wikistrat.

by J. N. Nielsen


Although we have spacecraft in orbit around Earth, as well as on the moon and other planets and their moons, and even spacecraft now in interstellar space, so that the products of human industry are to be found throughout our solar system and beyond, we have as yet no industrial infrastructure off the surface of the Earth, and this is important. I will try to explain how and why this is important, and why it will remain important, potentially shaping the structure of our civilization.

Made on Earth

All our spacecraft to date have been built on Earth where we possess an industrial infrastructure that makes this possible. The International Space Station, of course, was assembled in orbit from components built on the surface of the Earth and boosted into space on rockets. It has long been assumed, if we were to build a very large spacecraft (say, for a journey to Mars or beyond), that it would be constructed in much the same way: the components would be engineered on Earth and assembled in space. There is an obvious terrestrial analogy for this: we build our ships on land, where it is convenient to do the work, and then launch them only when the hull is seaworthy. Once the hull is in the water it is fitted out, and then come sea trials, but it would not be worth the trouble to try to build the hull of a ship in the water.

The analogy, however, seems misleading when applied to space. In space, we could build very large spacecraft in microgravity environments that would considerably ease the task of manipulating awkwardly large and heavy components. Also, large spacecraft never intended to enter into planetary atmospheres could be built in the vacuum of space with no concern for the aerodynamics that are crucial for a craft operating in a planetary atmosphere. The stresses of transiting a planetary atmosphere would be an unnecessary requirement for most deep-space vehicles. But what would it take to really build a spacecraft in space, in contradistinction to the assembly of completed modules in orbit?


Image: One take on building starships in space. This view of the Project Icarus orbital construction ring prototype design shows resupply from the Skylon single stage to orbit spacecraft now under development by Reaction Engines. Credit: Adrian Mann.

Even a “basic machine shop” in orbit would not come close to providing the kind of industrial infrastructure we have been building on the surface of the Earth for more than two hundred years now. Production processes ripple outward until they involve much of the planet’s industrial production capacity, a lesson that can be illustrated by Adam Smith’s famous example of the day-laborer’s woolen coat or by what Austrian economist Eugen Böhm von Bawerk called round-about production processes. [2] I suspect that many will argue that the advent of 3D printing is going to change everything, and that all you need to do is to boost a 3D printer into orbit and then you can produce anything that you might need in orbit. Well, not quite.

The Growth of Infrastructure

As civilization grows more complex, infrastructure becomes more complex, and more precursors are necessary to achieving the basic functionality assumed by the institutions of society. We see this in the increasing complexity of our cities. There was a time when cutting edge technology meant bringing water into a city with aqueducts and having underground sewers to carry away the waste. To the infrastructure of water supplies we have added fossil fuel supplies, electricity supplies, telecommunications lines, and now fiber optic cables for high speed internet access. (On the growing infrastructure of civilization cf. my post The Computational Infrastructure of Civilization.) All of these infrastructure requirements have been continually updated since their initial installation, so that, for example, the electricity grid is significantly more advanced today than when introduced.

For the lifeway of nomadic foragers, no infrastructure is necessary except for a knowledge of edible plants and available game. Since the geographical expansion of nomadic foragers is slow, change in requisite knowledge is also slow, as a moving band of foragers only very gradually sees the diminution of traditional dietary staples and only very gradually sees the emergence of unfamiliar plants and animals. Much greater infrastructure characterizes agrarian-ecclesiastical civilization, and much greater still industrial-technological civilization. The extraterrestrialization of industrial-technological civilization (yielding extraterrestrial-technological civilization) requires an order of magnitude of increase in infrastructure for the necessary maintenance of human life.

How to Build a Starship

The spacecraft requisite to the achievement of extraterrestrialization are today, and are likely to remain, the most complex and sophisticated machines ever built by human beings. To produce not only their components, but the machines required to produce the components, requires the entire advanced infrastructure that we now possess in our most developed centers of manufacturing. A useful analogy for understanding the industrial requirements for the production of spacecraft is to think of building the spacecraft of the future as we think today of building a nuclear-powered submarine. Like a nuclear submarine, an SSTO (single stage to orbit) spacecraft will be one of the most technically difficult and demanding engineering tasks ever attempted; it will involve parts suppliers from all over the world; it will involve millions of individual parts that each have to fitted in place by a human hand, and the assembly itself is likely to require many years of painstaking construction.

There is another sense in which spacecraft probably will be like nuclear submarines: a spacecraft is going to have significant power demands, and the most compact way to address this with our current technology is what we now do with your biggest submarines: nuclear power. The compact reactors on submarines (and aircraft carriers, which typically have two reactors for redundancy) have proved themselves to be safe and serviceable, and they can keep generating power for 25-30 years without refueling – possibly a sufficient period of time to make an interstellar journey. We can, of course, readily make use of solar power in space, though this is not compact and would not be suitable for a starship, which would be operating for extended periods of time far from the light of the sun or any other star.

I think it is clear that once we attain the ability to produce technologies commensurate to the challenge of a practicable starship, we are likely going to want to employ more than one propulsion technology, so that the drive system is highly hybridized. By “hybridized” I mean two or more forms of propulsion on a single spacecraft, and if these multiple forms of propulsion can share structures of the propulsion system, the more they do so the more truly “hybrid” the propulsion design. We may want to have one drive system for use in planetary atmospheres, another for orbital maneuvering, a third for interplanetary travel, and lastly a drive for interstellar travel. Later that list may need to be lengthened for a drive for intergalactic travel.

Hybrid propulsion systems are already in development, and these innovations could greatly improve the efficiency of chemical rockets. I have written many times about the Skylon spaceplane with its “combined cycle” SABRE engines that operate as conventional jet engines in the atmosphere, and which are able to transition to rocket propulsion for exoatmospheric operation. (Cf., e.g., Skylon spaceplane engine concept achieves key milestone, Key Tests for Skylon Spaceplane Project, Move to Open Sky for Skylon Spaceplace, and Addendum on Jet Propulsion Technology) This is a truly hybrid propulsion system, as the jet engine and chemical rocket share structures of the propulsion system, though it remains within the parameters of chemical rockets.

For faster travel to farther destinations, we will need hybrid propulsion systems of exotic technologies that do not exist today except in theory. A spacecraft with an Alcubierre drive and some basic form of chemical or nuclear or ion thrusters might be able to do the job, and this might well be the first step in building a starship that give us access to the galaxy in the way that we now have access to the surface of Earth. However, a spacecraft with an Alcubierre drive and a fusion or antimatter drive, or with Q-thrusters, would be much better. If, for example, you traveled to our closest cosmic neighbor, Alpha Centauri, you might want to travel the greater part of the distance with the Alcubierre drive, but once you get there you would probably want to make your passage between Proxima Centauri, Alpha Centauri A, and Alpha Centauri B with your fusion or antimatter drive, and you would definitely want to explore the planets of these stars with this “slower” drive. (And you probably wouldn’t want to use something like a Bussard ramjet for transit within a solar system.)

Two Responses to the Infrastructure Problem

A spacecraft mounting the kind of hybridized propulsion systems outlined above would represent an order of magnitude complexity even beyond the example of assembling a nuclear submarine. For the next few decades at least, and perhaps for longer, there will be no machine tools and no industrial plant in space. All the facilities we need to build a large and complex engineering project that is likely to occupy many years of painstaking effort, are earth-bound. Moreover, such technical assembly work would probably need to be performed by skilled craftsmen in a familiar environment conducive to careful and patient work. While there are significant advantages to constructing spacecraft in orbit, as noted above, the world’s most advanced industrial plant and best construction teams are on the earth and will be for some time, so that there remain compelling reasons for continuing to construct spacecraft on Earth, despite being at the bottom of a gravity well. This, in a nutshell, is the infrastructure problem.

There are two obvious responses to the infrastructure problem: (1) we accept the limitations of our industrial plant at face value and organize all space construction efforts around the assumption that spacecraft will be built on Earth, or (2) we begin the long task of constructing an industrial infrastructure off the surface of Earth. This latter approach may take as long as or longer than the building of our industrial infrastructure on Earth. While we have the advantage of higher technology and knowing what it is we want to produce, we also face the disadvantage of the harsh environment of space, and the need to initially boost from the surface of Earth everything not only required for industry, but also everything required for human life.

Almost certainly any human future in space will consist of some compromise between these two approaches, with the compromise tending either toward Earth-based industry or space-based industry. The model of extraterrestrialization that eventually prevails will not only be a matter of socioeconomic choice, but also a function of what is technological possible and what is technologically practicable. This latter requirement is insufficiently appreciated.

The Role of Contingency

The large-scale structure of human civilization, once it expands into space (provided we do not languish in permanent stagnation) will depend upon technological innovations that have not yet happened, and therefore the parameters of which are not yet known. That is to say, humanity as a spacefaring civilization is not indifferent to how we are able to travel in space, and how we are able to travel in space will be a result of the sciences we develop, the technologies that emerge from this science, and which among these technologies prove to be something that can be engineered into a practical vehicle, in terms of extraterrestrial transportation.

Just as we as a species are subject to contingencies related to the climatological conditions that shaped our evolution, the geography that has shaped our civilization, the gravity well of the Earth as a function of its mass that constrained our initial entry into space, and eventually the layout of our solar system as it will shape the initial spacefaring civilization that we can build in the vicinity of our own star, so too we are subject to contingencies that will arise out of our own actions (and inactions). These latter contingencies include the sciences we pursue, the technologies we develop, and the engineering of which we are capable. The human contingencies that determine the structure of our civilization in the future also include unknowns such as exactly which science, technology, and engineering projects get funding (cf. my recent post Why the Future Doesn’t Get Funded).

If it turns out that the science behind the Alcubierre drive concept is sound, and that this science can be the basis of a technology, and this technology can be engineered into a practicable starship, we may never construct an industrial infrastructure in space. It may prove to be easier to construct starships not as massive works slowly assembled in Earth orbit, but rather as relatively compact spacecraft constructed in the convenience of a hangar, which, once finished, can be rolled out onto the tarmac, fired up, and blasted into space, thence to activate its Alcubierre drive once in orbit in order to fly off to other worlds. If, in addition, habitable planets (or planets that can be made habitable) are not too rare in the Milky Way, and human beings prefer to spend their time planetside, the industrialization of space may never occur. In this scenario, space-based industry always remains marginal, even as we become a spacefaring civilization.

As it is, we already today seeing the beginnings of the gradual transition of our industrial infrastructure into something cleaner than the smoke-belching chimneys of the early industrial revolution. As this process continues, and we continue to improve the efficiency of solar cells, there may be little or no economic benefit for moving industry into space. We may pass a threshold, beyond which Earth-based industry can be made entirely benign, therefore obviating the need to move industry into space. But all of this hinges on unknowns of an eminently practical sort, and which we cannot predict until we have actual experience operating the technologies in question.

Space-Based Infrastructure and Planetary-Based Infrastructure

If the Alcubierre drive turns out to be impracticable, or even not practicable at technological levels of development obtainable in the next few hundred years, then the need to construct different kinds of spacecraft will be more pressing. The idea of building a sleek spacecraft in a hangar and blasting off to other worlds directly from Earth’s surface may be impossible. In this case, becoming a spacefaring species, and especially becoming a starfaring species, will likely mean the construction of enormous industrial works off the surface of the Earth, initially assembling large spacecraft in Earth orbit or beyond, but gradually providing more and more goods and services in space without having to boost them all from the ground, which means the industrialization of space.

The industrialization of space, in turn, would mean a very different kind of large-scale spacefaring civilization than a spacefaring civilization that had no need of the industrialization of space, as described in the examples above. A spacefaring civilization of primarily space-based industry would be distinct from a spacefaring civilization of primarily planetary-based industry. Distinct social, political, and economic institutions and imperatives would emerge from these distinct industrial infrastructures.

If, as Marx claimed, ideological superstructures follow from the economic infrastructure that the former emerge to justify, [3] then it is to be expected that space-based economic infrastructure will produce an ideological superstructure distinct from planetary-based economic infrastructure. In the distant future, when we have occasion to survey many different spacefaring civilizations, this may prove to be a fundamental distinction that divides them.


[1] At the Icarus Interstellar Starship Congress last year, a member of the audience asked a question of Kelvin Long in which the questioner used the phrase, “the infrastructure problem,” which strikes me as the perfect formulation for the topics I am covering today.

[2] On Adam Smith’s example of the day-laborer’s woolen coat cf. Smith’s The Wealth of Nations, the final paragraph of Book I, chapter 1; on round-about production processes in the work of Eugen Böhm von Bawerk, cf. Thesis 22 of my book Political Economy of Globalization.

[3] The locus classicus for this Marxian view is to be found in Marx’s A Contribution to The Critique of Political Economy, translated from the Second German Edition by N. I. Stone, Chicago: Charles H. Kerr & Company, 1911, Author’s Preface, pp. 11-12: “In the social production which men carry on they enter into definite relations that are indispensable and independent of their will, these relations of production correspond to a definite stage of development of their material powers of production. The sum total of these relations of production constitutes the economic structure of society — the real foundation, on which rise legal and political superstructures and to which correspond definite forms of social consciousness. The mode of production in material life determines the general character of social, political, and spiritual processes of life. It is not the consciousness of men that determines their existence, but, on the contrary, their social existence determines their consciousness.” Note that Marx usually refers to the “economic base” of a society rather than to its “economic infrastructure.”


55 Cancri A: Stable Orbital Solutions

We’re developing a model for the fascinating planetary system around the binary star 55 Cancri, a challenging task given the complexity of the inner system in particular. What we have here is a G-class star around which five planets are known to orbit and a distant M-dwarf at over 1000 AU. Have a look at the diagram below and you’ll see why the system, 39 light years away in the constellation Cancer, draws so much attention. It’s much more than the fact that direct measurements of the G-class star’s radius are possible at this distance, which have led to precise measurements of its mass, about the same as our Sun. It’s also the tightly packed configuration of the inner planets.


Image: An illustration of the orbital distances and relative sizes of the four innermost planets known to orbit the star 55 Cancri A (bottom) in comparison with planets in own inner Solar System (top). Both Jupiter and the Jupiter-mass planet 55 Cancri “d” are outside this picture, orbiting their host star with a distance of nearly 5 astronomical units (AU), where one AU is equal to the average distance between the Earth and the Sun. Credit: Center for Exoplanets and Habitable Worlds, Penn State University.

First discovered to be orbited by a giant planet in 1997, 55 Cancri A has been the subject of numerous studies in the years since. We have five planets in total, one a cold gas giant evidently similar to Jupiter and in a similar orbit and another, of particular interest, a ‘super-Earth’ in close proximity to the host star. This world, 55 Cancri e, was thought until 2011 to orbit the star in three days, but astronomers then determined that its complete orbit took less than 18 hours. The software developed by Penn State graduate student Benjamin Nelson and Eric Ford (Penn State Center for Astrostatistics) has pegged the mass of 55 Cancri e at eight Earth masses.

A quick note on nomenclature: The formal designation for the innermost world here should be 55 Cancri A e, with the other planets referred to accordingly. I’m following the just published paper on this work in referring to it as 55 Cancri e, without reference to the distant M-dwarf.

The transiting world is now known to have a radius twice that of Earth and a density about the same as our planet. Another glance at the diagram shows that this is a world far too hot for life as we know it, reaching temperatures in the range of 2300 Kelvin. The computations of Nelson and Ford draw the details of 55 Cancri e out of the motions of the giant planets 55 Cancri b and c, worlds that although orbiting outside the orbit of 55 Cancri e are still located closer to the star than Mercury is to our Sun. The new techniques help us understand how large planets like these can orbit so close to their star without collision or the expulsion of one of the two worlds.

The motion of the inner giant planets has to be accounted for to measure the detailed properties of the ‘super-Earth,’ and Ford notes that most previous work on this system had ignored their interactions. Nelson explains the significance of understanding the stability of their orbits:

“These two giant planets of 55 Cancri interact so strongly that we can detect changes in their orbits. These detections are exciting because they enable us to learn things about the orbits that are normally not observable. However, the rapid interactions between the planets also present a challenge since modeling the system requires time-consuming simulations for each model to determine the trajectories of the planets and therefore their likelihood of survival for billions of years without a catastrophic collision.”

1418 radial velocity observations from four observatories went into this work along with transit studies for 55 Cancri e, out of which orbital solutions stable for a minimum of 108 years emerge. The researchers evolved four- and five-planet models as they examined instabilities in the system, coupling their work with radial velocity observations to constrain the planet masses and orbital parameters that produce dynamically stable solutions. As the paper notes, “By combining a rigorous statistical analysis, dynamical model and improved observational constraints, we obtain the first set of five-planet models that are dynamically stable.” Another interesting finding: 55 Cancri d turns out to be “the closest Jupiter analog to date” in terms of orbital period and eccentricity.

The paper is Nelson et al., “The 55 Cancri Planetary System: Fully Self-Consistent N-body Constraints and a Dynamical Analysis,” Monthly Notices of the Royal Astronomical Society, published online 22 April 2014 (preprint). Also see this Penn State news release.